‘Hub’-bub: World Trade Center Transportation Hub is a sight to behold — but how functional is it?

This first peek at the WTC transit hub is architecturally spectacular, but how useful its underground passageways will be is doubtful. Gabriella Bass

The World Trade Center Transportation Hub — six years late and nearly $2 billion over budget — is finally starting to look like a “bird in flight.”

Or is it a scary spaceship like the ones in the Alien movies?

With the Santiago Calatrava-designed project’s “wings” finally sprouting from the ground, the Port Authority yesterday offered us a first look inside the belly of the beast — the $3.9 billion transit complex that will link the PATH station with 13 subway lines, the MTA’s new Fulton Center, WTC office buildings and stores, the World Financial Center and Winter Garden, and just maybe the New Jersey Palisades.

For the first time, we stood inside the now roof-less Oculus, the subterranean transit hall big enough to swallow Grand Central Terminal with a 365-foot-long floor, an arched, 160-foot-high ceiling and framed by exterior “wings” rising to 250 feet.

We ventured deeper underground into the PATH Hall — a second endless concourse New Jersey commuters must traverse to reach trains. If the Oculus suggests a whale’s stomach with its soaring steel ribs, the Hall’s snaking, pipe-like ceiling evokes the spacecraft where creatures from hell ate Sigourney Weaver’s mates alive.

Two years before its rescheduled 2015 opening, the hub still has a long way to go before it looks anything like renderings we’ve all seen. Even now, though, it’s undeniably an astonishing — perhaps heroic — feat of architectural engineering.

It’s impossible to stand in its midst and not be moved by the sheer magnitude of talent, energy and determination that have brought the Hub this far. No wonder it’s costing more than anything else at “Ground Zero,” more even than the soaring 1 WTC.

But is this pet project of the PA’s New Jersey side worth it?

The Hub’s so big, complicated and densely packed with everything all around, it made three skyscrapers and the Memorial much harder and costlier to build.

And how many will use it? More than 250,000 daily, PA construction chief Steve Plate said yesterday. Skeptics say as few as 50,000, mostly Jersey commuters. The project adds no new track, only endless underground corridors for walking from here to there. Isn’t that what city streets are for?